So, if you're not prepared to live with potential bugs, bear in mind you can't run both side-by-side. It's also important to note that installing the Office 2016 preview will overwrite any current Office installs on your machine.
'Once the trial period expires, you will have the option to purchase an Office 365 subscription or reinstall your current version using your original product key.' You will stay on the Office 2016 Preview track until you uninstall the Office 2016 Preview or until Office 2016 is released.' 'This will install the Office 2016 Preview on your device.
Microsoft describes both scenarios as such: If you're not an Office 365 subscriber then you'll just need to download the package from Microsoft: VPN Deals: Lifetime license for $16, monthly plans at $1 & more For everyone else
